Lifting mechanism for industrial trucks



May 30, 1950 G. QUAYLE 2,510,037

LIFTING MECHANISM FOR INDUSTRIAL TRUCKS Filed July 8, 1946 2 Sheets-Sheet 1 m a NVENTOR Geogz Q asi ATTORNEY y 1950 G. QUAYLE 2,510,037

LIFTING MECHANISM FOR INDUSTRIAL TRUCKS Filed July 8, 1946 2 Sheets-Sheet 2 INVENTOR Ge ar e Q a ATTO R N EY Patented May 30, 1950 LIFTING MECHANISM FOR INDUSTRIAL TRUCKS George Quayle, Philadelphia, Pa., assignor to The Yale & Towne Manufacturing Company, Stamford, 002111., a corporation of Connecticut Application July 8, 1946, Serial No. 681,885

11 Claims. 1

This invention relates to a lift truck, and more particularly a lift truck of the type disclosed in my earlier application, Ser. No. 468,715 filed December 11, 1942 now Patent No. 2,405,848. The truck of my earlier application is of that class known in the art as a mechanical lifting single frame truck. Thus, the truck is equipped with a, lifting head having lifting mechanism, and pivoted to this lifting head through support links is the front end of an elevatin platform, the elevating platform being supported at its rear end by wheels mounted on links pivoted to the elevating platform. This type of truck is called a single-frame truck because the elevating platform is really the only frame of the truck and is self-supported and self-lifting through its rear wheels. This truck may be distinguished readily from two-frame trucks, because two-frame trucks have a main frame that is wheel-supported, front and rear, and have mounted thereon through front and rear links an elevating platform.

It is the object of this invention to contribute to the art a mechanical lifting single-frame truck in which the elevating platform constituting the sin le frame is lifted, and preferably maintained lifted also, through the intermediary of a spring mechanism. I have heretofore contributed to the art lift trucks in which the elevating platform is raised and maintained in an elevated position through the intermediary of spring mechanism, but in all such trucks it has been possible to do this by a spring located in the lifting apparatus per se. An arrangement of this type is not effective in a mechanical lifting single-frame truck, and it is for that reason that the problem has long confronted the art without solution.

It is a feature of my invention that the actuation of the lifting wheels at the rear of the elevating platform is accomplished through the intermediary of spring mechanism. A further feature of the invention resides in the utilization of one of the mounting links for the elevating platform as the actuating means for the spring mechanism.

A further feature of the invention resides in means whereby the spring mechanism may be maintained under some initial compression at all times so as to minimize the work necessary to lift the elevating platform.

I have thus outlined rather broadly the more important features of my invention in order that the detailed description thereof that follows may be better understood, and in order that my con tribution to the art may be better appreciated. There are, of course, additional features of my invention that will be described hereinafter and which will form the subject of the claims appended hereto. Those skilled in the art will ap preciate that the conception on which my disclosure is based may readily be utilized by those skilled in the art as a basis for the designing of other structures for carrying out the several purposes of my invention. It is important, therefore, that the claims to be granted me shall be of suflicient breadth to prevent the appropriation of my invention by those skilled in the art. I

Referring now to the drawings, Fig. 1 :is an elevation of the lift truck of my application supra, showing my invention applied thereto. Fig. 2 is a vertical section taken along lines 2-2 of Fig. 3, Fig. 3 being itself a plan View of the main portion of the elevating platform of the truck.

Referring now more particularly to the drawings, reference numeral It indicates generally a lifting head having a forward supporting and steering wheel II rotatable relatively to the lifting head through means of what I term a steering head I2. A steering and lifting handle I3 is pivoted at I4 on the steering head I2 and is adapted to actuate suitable lift mechanism generally designated by reference letter L. This lift mechanism is well illustrated and described in my application supra and does not form per se the invention of this application. As a matter of fact, any type of mechanical lifting mechanism may be used to lift the forward end of my elevating platform. It is because this type of mechanism does not lend itself to use with an interposed spring that the invention of this application is so important.

The elevating platform of my truck is designated by reference numeral I5 and is formed with a front vertical standard IE. This vertical standard is pivoted to the lifting head II] by what is in effect an upper link I! and a lower link I8. The upper link is pivoted to the lifting head I0 on an axis I9 and to the elevating platform on an axis 20. The lower lifting link I8 comprises a pair of plates 2| best shown in Fig. 3. These plates 2I are pivoted at their forward end by a shaft 22 relatively to ears 23 extending from the lifting head I0 and forming an integral part thereof. The plates 2i are pivoted to the elevating platform l5 by means of trunnions 24. It is, of course, obvious, that a line extending from the axis of shaft 22 toward the axis of the trunnions 24 will be parallel to a line extending between axes I9 and 20 of the upper link IT. The elevating platform will, therefore, move upwardly on the links I! and I8 when upward lifting movement is imparted to the elevating plat form by the lift mechanism L, all as is fully and clearly set forth in my earlier application.

Extending between the plates 2! of the link I8 is a shaft 25, and pivoted on this shaft 25 is what might be termed an actuating member 26.

The actuating member 26 has secured thereto in adjustable threaded relation a tension rod 21. At its other end the tension rod 21 is threaded at 28 to be adjustably secured by a nut Z'la to a spring actuating member designated generally by reference numeral 29. Spring actuating member 29 comprises a central portion 39 to which the tension rod 2! is secured, and comprises further a pair of sleeves 3! formed integrally with the part 30 and mounted about rods 32 for sliding movement on the said rods.

Rods 32 are in turn secured, as by Welding, to

V a plate 33 that is welded at one end to a sleeve 34. Through the said sleeve 34, and by means ofroller bearings 35, the plate 33 is pivoted to a shaft ffi-that xt nds be ween a pa r o plate c n.- stitutin a re rwh lsunpo t ns l ku t plat s 3, ar w l ed to rm n inte r l. p r eeve 38. arryin n, a le 39 on wh h re mounted the rear wheels 41 of he ruc h pla es 3'! r pivoted r iv ly to he v in pl tform. by mean f. a shaft i supp rt d at 4! and 42 on the frame of'the elevatingplatform l5.

Referring back once again to the rods 32 that are. an integral part of the plate 33, we find that these rods are adjnstablysecured at their extrerne right ends tq a limit plate 43, a pair of nuts 4 l m in he oveme t of th p ate 4 to the right in. Fig 3 relatively to the rods 32. A spring 45 is mounted about each of the sleeves 3! and bears at its right end against the plate 43 and at its left end against a plate 45 forming part o he sp ng a uating m er It is obvious. that by adjusting nuts 44 and the nut 21g bearing against part 30 of spring actuating member 29, it is possible to place springs under an initial compression for a purpose presnt to e sc ed,

Having now described the parts of my invention, it, will be well to indicate the operation thereof utilized for the lifting of the elevating platform through means of the springs 45, and for thereafter maintaining the elevating platf m te by e s dsnrinss- When the elevating platform is in its full line position of Fig. 1, andin the position of Fig. 2, the lifting wheels 41 and plates 3'! constituting the rear wheel supporting link are in a position holding the elevating platform lowered relatively to the lifting head. Operation of the steerin and lifting handle I3, as is fully set forth in my earlier application, will act to bring the forward end of the elevating platform into its dash and dotted line position of Fig. 1, this movement being accomplished by the swinging of the platform on links ll and it. It will be seen that jas the link [8 moves into its dash and dotted line position of Fig. 1 it will impart movement to the actuating member 26 for moving the tension rod- 21 to the right from its position of Figs. 2 and 3, lhis movement of the tension rod 27 will act through the spring actuating member 29 to apply compression to the springs 65. This compression will be accepted by the limit plate d3 which will in turn move the rods 32 to the right from the position of Fig. 3. This movement will actuate the plate 33 which through the shaft 36 will rotate the plates 37. Rotation of plates 31 will, of course, effect an upward lifting movement to the shaft ill and a consequent upward lifting movement of the rear end of the elevating platform.

In the event of any weakening of a spring 45, as when an excessive load is to be raised, the

ends 3la of the sleeves 3| will be applied to the limit plate 43 so as to actuate that plate directly instead of through the intermediary of the springs 65. It is also to be noted that because springs 45 are under some initial compression, less movement of rod 2'! is required to move plate 33 than if the springs required full compression. This is a very important feature as it decreases the amount of movement of the lifting mechanism required tolift the elevating platform.

Those skilled in the art will now appreciate that lifting movement imparted to plates 31 of the rear wheel supporting link through the intermediary'of a spring mechanism, and that the said plates 3'! are maintained in platform lifting position through the intermediary of a spring mechanism. Thus, it is apparent. that solong as 'the if ing m n sm. main ains oforwardd of the e evatin lat rm in itsra sed. position, the od 21. wil m ntain e p n 5 omrrossed to h d he re r end o he elevatin platform in its. raised positio It ma be w lltth s nt to indica e that. while .1 hav i l s ted m n,- vention applied to the structure of my earlier ap l cat on a d it regard to a, n ram uck of t e t pe w ch t o le t ne pla rm is pivoted relatively to the lifting head, my invention is applicable to other types of trucks and to trucks in whioh the elevating platform is mount: ed for movement other than pivotal relatively to the lifting head.

I now claim:

1. In a truck of the class described, an elevating platform, a lifting head, a forward link pivotally mounting said elevating platform for up- Ward swinging movement relatively to said lifting head, a wheel mounting link pivoted to the rear end of said elevating platform, a tension member pivoted to saidv forward link, a rod pivoted to, said wheel mounting link, a spring about said rod, pressing. at oneend thereof against alimit, member secured to said rod, and means whereby said tension member applies compressive force a id p n to move. i imit member. and rod through the intermediary of said spring when said tension member and forward link move incidental to the lifting of the forward end of said elevating platform.

2. In a truck of the class described, an elevating platform, a lifting head, means mounting said elevating platform for upward movement relatively to said lifting head, a wheel mounting link pivoted to the rear end of said elevating platform, a tension member, lifting means for applying tension to said tension member, a rod secured to said wheel mounting link, a spring about said rod pressingat one end thereofagainst'a limit member secured to said rod, and means whereby said tension member applies compressive force against said spring to move said limit member and rod through the intermediary of said spring when tension is applied to said tension member.

3. In a truck of the class described, an elevating platform, a lifting head,'a forward link pivotallymountingsaid elevating platform for upward swinging movement relatively to said lift ing head, a wheel mounting link pivoted to the rear end of said elevating platform/a tension member pivoted to said forward link; a rod pivoted to said wheel mounting link, a, spring about said rod pressing at one end thereof against 'a limit member secured to said'rod,'and means whereby said tension member applies compressive force against said spring to move said limit member and rod" through the intermediary of said spring when said tension member and forward.

link move incidental to the lifting of the forward end of said elevating platform, said means app ing force directly against said limit member after predetermined compression of said spring.

4. In a truck of the class described, an elevating platform, a lifting head, means mounting said elevating platform for upward movement relatively to said lifting head, a wheel mounting link pivoted to the rear end of said elevating platform, a tension member, lifting means for imparting tension to said tension member, a rod secured to said wheel mounting link, a spring about said rod pressing at one end thereof against a limit member secured to said rod, and means whereby said tension member applies compressive force against said spring to move said limit member and rod through the intermediary of said spring when tension is applied to said tension member, said means applying force directly against said limit member after predetermined compression of said spring.

5. In a truck of the class described. an elevating platform, a lifting head, a forward link plyotally mounting said elevating platform for upward swinging movement relatively to said lift ing head, a wheel mounting link pivoted to the rear end of said elevating platform, a tension member pivoted to said forward link, a pair of parallel rods pivoted at one end thereof to said wheel mo ntin link, a spring about each rod, a limit member secured to the other ends of said rods. and means whereby said tension member applies compressive force against said springs to move said limit member and rods through the intermediary of said springs when said tension mem er and forward link move incidental to the lifting of the forward end of said elevating platform.

6. In a truck of the class described, an elevating platform, a lifting head, a forward link pivotally mounting said elevating platform for upward swinging movement relatively to said lifting head, a wheel mounting link pivoted to the rear end of said elevating platform, a tension member pivoted to said forward link, a pair of parallel rods pivoted at one end thereof to said wheel mounting link, a spring about each rod, a limit member secured to the other ends of said rods, and means whereby said tension member applies compressive force against said springs to move said limit member and rods throu h the intermediary of said springs when said tension member and forward link move incidental to the lifting of. the forward end of said elevating platform, said means applying force directly against said limit member after predetermined compression of said spring,

'7. In a lifting truck of the class described. an elevating platform, a lifting head. means mounting the forward end of said elevating platform for upward movement relatively to sa d lifting head a wheel mounting link pivoted to the rear end of said elevating platform, a lifting wheel on said link, actuating means for rotating said link on its pivot to lift the rear end of said elevating platform, means for moving said actuating means operated upon upward movement of the forward end of said elevating platform relatively to said lifting head, and a spring through which said means moves said actuating means, the compression of said spring to a predetermined degree bringing said means into physical contact with said actuating means for moving said actuating means without the interposition of said spring.

8. In a lifting truck of the class described, an

elevating platform, a lifting head, means mounting the forward end of said elevating platform for upward movement relatively to said lifting head, a wheel mounting element pivoted to the rear end of said elevating platform, a lifting wheel on said element, an actuating element for rotating said wheel mounting element on its pivot to lift the rear end of said elevating platform, an operating element for moving said actuating element operated upon upward movement of the forward end of said elevating platform relatively to said lifting head, and a spring interposed between at least two of said elements whereby the rear end of said elevating platform is lifted through the intermediary of said spring, the compression of said spring to a predetermined degree bringing said elements into physical contact for lifting said elevating platform without the intermediary of a spring.

9. in a truck of the class described, an elevating platform, a lifting head, means mounting said elevating platform for upward movement relatively to said lifting head, a wheel mounting link pivoted to the rear end of said elevating platform, a tension member, lifting means for imparting tension to said tension member, a spring, means holding said spring in position for compression relatively to said lifting link to rotate said lifting link, means whereby said tension member applies compressive force to said spring to rotate said lifting link, and adjustable means for maintaining said spring under predetermined initial compression.

10. In a truck of the class described, an elevating platform, a lifting head, means mounting said elevating platform for upward movement relatively to said lifting head, a wheel mounting link pivoted to the rear end of said elevating platform, a tension member, lifting means for applying tension to said tension member, a rod secured to said wheel mounting link, a spring about said rod pressing at one end thereof against a limit member secured to said rod, means whereby said tension member applies compressive force against said spring to move said limit member and rod through the intermediary of said spring, and adjustable means for maintaining said spring under predetermined initial compression.

11. In a truck of the class described, an elevating platform, a lifting head, a forward link pivotally mounting said elevating platform for upward swinging movement relatively to said lifting head, a wheel mounting link pivoted to the rear end of said elevating platform, a tension member pivoted to said forward link, a rod pivoted to said wheel mounting link, a spring about said rod pressing at one end thereof against a limit member secured to said rod, means whereby said tension member applies compressive force against said spring to move said limit member and rod through the intermediary of said spring, and adjustable means for maintaining said spring under predetermined initial compression.

GEORGE QUATYLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,355,328 Quayle Aug. 8, 1944 2,367,051 Quayle Jan. 9, 1945 2,367,961 Schroeder Jan. 9, 1945 2,369,854 Quayle Feb. 20, 1945 2,399,596 Framheim Apr. 30, 1946 

